The present invention relates to bone joint prostheses and more particularly to a prosthesis for the total replacement of a hinge type bone joint and which results in stable flexion and extension movements.
The bones of the human skeleton are joined by a variety of different bone joints. Joints may be classified into two main structural types, namely diarthroses and synarthroses. Diarthroses are joints having a joint cavity between the articulating surfaces of the bones. Synarthroses are joints which have tissues growing between their articulating surfaces. The tissue does not permit free movement between the articulating surfaces.
Diarthrotic joints besides having a joint cavity include a thin layer of hyaline cartilage covering the joint surfaces of the articulating bones. A sleeve-like, fibrous capsule lined with a smooth, slippery synovial membrane encases the joint. Ligaments grow between the bones to constrain and latch the bones firmly together. Diarthrotic joints permit one or more of a variety of movements including flexion, extension, abduction, adduction, rotation, circumduction and special movements such as supination, pronation, inversion, eversion, protraction and retraction.
The broad joint classification may be broken down into subtypes based upon the structural relationship of the bones at the joints and the movements involved. These subtypes include the ball and socket joint, the hinge or ginglymous joint, the pivot or trochoid joint, the condyloid joint, the saddle joint and the gliding or arthrodial joint.
Procedures have been developed for repairing severely diseased or damaged joints when significant stiffness, pain or loss of motion is present. These procedures have included arthroplasty, that is, removal of the defective bone portions and partial implant replacement, which essentially involves resurfacing of one of the articulating bone surfaces with a prosthesis. Fairly recently, total joint prostheses have been developed which entirely replace the joint. Such prosthetic devices have been employed for replacement of finger joints, knee joints and elbow joints, for example.
The elbow is a diarthrotic joint formed by articulation of the distal humerus with both the radius and the ulna. Stability depends on the shape of the joint articular surfaces and the maintenance of their coaptation by the ligaments and muscles surrounding the joint. A hinge joint exits at the ulnar humeral articulation allowing movement of flexion and extension only. The articulation between the radius and the humerus is a trochoid or pivot joint which allows nearly all movements of pronation and supination of the forearm. The distal humerus includes the trochlea which articulates with the semilunar notch of the ulna and the capitulum which articulates with the proximal surface of the radial head. The vertical margin of the radial head rotates with the radial notch of the ulna.
Repair of diseased or damaged elbow joints has included resection arthroplasty, implant replacement of the radial head, flexible implant resection arthroplasty of the elbow joint and the use of rigid metal hinge devices for arthroplasty of the elbow joint. Reconstitution with prior hinge type total prostheses has presented various problems relating to stability of the joint, loosening of the implant, excessive bone stock removal and transmission of excessive stress to the bones by the implant.
A discussion of the problems heretofore experienced and examples of some prior approaches may be found in Alfred B. Swanson, Flexible Implant Resection Arthroplasty In the Hand and Extremities pp. 265-286 (1973).
Prior total elbow procedures have also typically included resection of the radial head. Proximal migration of the radial shaft may occur. Such migration typically results in limitations of wrist motion, radial deviation of the hand, and prominence of the distal end of the ulna. These result in pain, instability, weakness, tiredness and a limitation on range of motion. With rheumatoid arthritis patients, postoperative complications at the wrist after radial head resection have been or may be overlooked. Such pathology is imputed to the generalized disease.
Further examples of prior elbow joint prostheses may be found in U.S. Pat. No. 3,852,831, entitled ENDOPROSTHETIC ELBOW JOINT and issued on Dec. 10, 1974 to Dee; U.S. Pat. No. 3,990,118, entitled JOINT PROSTHESIS and issued on Nov. 9, 1976 to Stickland et al; U.S. Pat. No. 4,057,858, entitled ELBOW PROSTHESIS and issued on Nov. 15, 1977 to Helfet; U.S. Pat. No. 4,079,469, entitled ELBOW JOINT ENDOPROSTHESIS and issued on Mar. 21, 1978 to Wadsworth; and U.S. Pat. No. 4,131,956, entitled ELBOW PROSTHESIS and issued on Jan. 2, 1979 to Treace.
The prosthesis disclosed in U.S. Pat. No. 4,079,469 includes a humeral component hinged by a T-slot structure to an ulnar component. The humeral component defines a lateral, hemispherical surface which replaces the capitulum. The head of the radius, which may have a head implant thereon, articulates with the hemispherical surface.
Despite the wide variety of proposals and procedures available for replacement of joints such as the elbow joint, problems have still been experienced and a need exists for an improved hinge joint possessing increased stability, which reduces the stress and strain imposed upon the adjacent bones and which simplifies the surgical procedure.